A relational database includes a collection of tables of data items formally described and organized according to the relational model for database management. The relational model is based on first-order predicate logic, whereby the data items are represented in terms of tuples grouped into relations. Often, data items from multiple tables are combined using a join operation. Using a relational database management system (RDBMS), users and programs may request data from a relational database by performing a query that is written in a special language, usually a dialect of the Structured Query Language (SQL). After receiving the query, the RDBMS may rewrite or transform predicates in the query to optimize a search for the requested data items.